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Date: Wed, 18 Jan 2017 14:32:39 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Cao jin <caoj.fnst@...fujitsu.com>, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org, qemu-devel@...gnu.org,
izumi.taku@...fujitsu.com
Subject: Re: [PATCH v2] vfio/pci: Support error recovery
On Tue, 10 Jan 2017 17:11:01 +0200
"Michael S. Tsirkin" <mst@...hat.com> wrote:
> On Tue, Jan 10, 2017 at 07:46:17PM +0800, Cao jin wrote:
> >
> >
> > On 01/10/2017 07:04 AM, Michael S. Tsirkin wrote:
> > > On Sat, Dec 31, 2016 at 05:15:36PM +0800, Cao jin wrote:
> > >> Support serious device error recovery
> > >
> > > serious?
> > >
> >
> > Sorry for my poor vocabulary if it confuses people. I wanted to express
> > the meaning that: vfio-pci actually cannot do a real recovery for device
> > even if it provides the callbacks, it relies on the user to do a
> > effective(or word "serious"?) recovery.
> >
> > Welcome the amendment on the commit log.
>
> It's up to Alex, maybe he's able to figure it all out from
> code, but the rest of us could benefit from a description
> of what the patch does from userspace point of view.
>
> Also, is it a pre-requisite of the userspace patches you posted?
This is the same blocking user accesses while the device is in recovery
that you thought was ineffective/wrong before. Why do we still need it
if QEMU isn't trying to handle fatal errors? If the kernel is doing a
reset shouldn't the user consider the device dead? A commit log
explaining this is absolutely necessary. Thanks,
Alex
> > >>
> > >> Signed-off-by: Cao jin <caoj.fnst@...fujitsu.com>
> > >> ---
> > >> drivers/vfio/pci/vfio_pci.c | 70 +++++++++++++++++++++++++++++++++++--
> > >> drivers/vfio/pci/vfio_pci_private.h | 2 ++
> > >> 2 files changed, 70 insertions(+), 2 deletions(-)
> > >>
> > >> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> > >> index 712a849..752af20 100644
> > >> --- a/drivers/vfio/pci/vfio_pci.c
> > >> +++ b/drivers/vfio/pci/vfio_pci.c
> > >> @@ -534,6 +534,15 @@ static long vfio_pci_ioctl(void *device_data,
> > >> {
> > >> struct vfio_pci_device *vdev = device_data;
> > >> unsigned long minsz;
> > >> + int ret;
> > >> +
> > >> + if (vdev->aer_recovering && (cmd == VFIO_DEVICE_SET_IRQS ||
> > >> + cmd == VFIO_DEVICE_RESET || cmd == VFIO_DEVICE_PCI_HOT_RESET)) {
> > >> + ret = wait_for_completion_interruptible(
> > >> + &vdev->aer_completion);
> > >
> > > don't split it like that.
> > >
> > >> + if (ret)
> > >> + return ret;
> > >> + }
> > >>
> > >> if (cmd == VFIO_DEVICE_GET_INFO) {
> > >> struct vfio_device_info info;
> > >> @@ -953,6 +962,15 @@ static ssize_t vfio_pci_rw(void *device_data, char __user *buf,
> > >> {
> > >> unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> > >> struct vfio_pci_device *vdev = device_data;
> > >> + int ret;
> > >> +
> > >> + /* block all kinds of access during host recovery */
> > >> + if (vdev->aer_recovering) {
> > >> + ret = wait_for_completion_interruptible(
> > >> + &vdev->aer_completion);
> > >> + if (ret)
> > >> + return ret;
> > >> + }
> > >>
> > >> if (index >= VFIO_PCI_NUM_REGIONS + vdev->num_regions)
> > >> return -EINVAL;
> > >> @@ -1117,6 +1135,7 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> > >> vdev->irq_type = VFIO_PCI_NUM_IRQS;
> > >> mutex_init(&vdev->igate);
> > >> spin_lock_init(&vdev->irqlock);
> > >> + init_completion(&vdev->aer_completion);
> > >>
> > >> ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
> > >> if (ret) {
> > >> @@ -1176,6 +1195,9 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
> > >> {
> > >> struct vfio_pci_device *vdev;
> > >> struct vfio_device *device;
> > >> + u32 uncor_status;
> > >> + unsigned int aer_cap_offset;
> > >> + int ret;
> > >>
> > >> device = vfio_device_get_from_dev(&pdev->dev);
> > >> if (device == NULL)
> > >> @@ -1187,10 +1209,29 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
> > >> return PCI_ERS_RESULT_DISCONNECT;
> > >> }
> > >>
> > >> + /*
> > >> + * get device's uncorrectable error status as soon as possible,
> > >
> > > should be "Get".
> > >
> > >> + * and signal it to user space. The later we read it, the possibility
> > >> + * the register value is mangled grows.
> > >> + */
> > >> + aer_cap_offset = pci_find_ext_capability(vdev->pdev, PCI_EXT_CAP_ID_ERR);
> > >> + ret = pci_read_config_dword(vdev->pdev, aer_cap_offset +
> > >> + PCI_ERR_UNCOR_STATUS, &uncor_status);
> > >> + if (ret)
> > >> + return PCI_ERS_RESULT_DISCONNECT;
> > >> +
> > >> + pr_info("device %d got AER detect notification. uncorrectable error status = 0x%x\n", pdev->devfn, uncor_status);//to be removed
> > >
> > > Pls drop this.
> > >
> > >> mutex_lock(&vdev->igate);
> > >>
> > >> - if (vdev->err_trigger)
> > >> - eventfd_signal(vdev->err_trigger, 1);
> > >> + vdev->aer_recovering = true;
> > >> + reinit_completion(&vdev->aer_completion);
> > >> +
> > >> + if (vdev->err_trigger && uncor_status) {
> > >> + pr_info("device %d signal uncor status 0x%x to user",
> > >> + pdev->devfn, uncor_status);
> > >> + /* signal uncorrectable error status to user space */
> > >> + eventfd_signal(vdev->err_trigger, uncor_status);
> > >> + }
> > >>
> > >> mutex_unlock(&vdev->igate);
> > >>
> > >> @@ -1199,8 +1240,33 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
> > >> return PCI_ERS_RESULT_CAN_RECOVER;
> > >> }
> > >>
> > >> +static void vfio_pci_aer_resume(struct pci_dev *pdev)
> > >> +{
> > >> + struct vfio_pci_device *vdev;
> > >> + struct vfio_device *device;
> > >> +
> > >> + device = vfio_device_get_from_dev(&pdev->dev);
> > >> + if (device == NULL)
> > >> + return;
> > >> +
> > >> + vdev = vfio_device_data(device);
> > >> + if (vdev == NULL) {
> > >> + vfio_device_put(device);
> > >> + return;
> > >> + }
> > >> +
> > >> + mutex_lock(&vdev->igate);
> > >> + vdev->aer_recovering = false;
> > >> + mutex_unlock(&vdev->igate);
> > >> +
> > >> + complete_all(&vdev->aer_completion);
> > >> +
> > >> + vfio_device_put(device);
> > >> +}
> > >> +
> > >> static const struct pci_error_handlers vfio_err_handlers = {
> > >> .error_detected = vfio_pci_aer_err_detected,
> > >> + .resume = vfio_pci_aer_resume,
> > >> };
> > >>
> > >> static struct pci_driver vfio_pci_driver = {
> > >> diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
> > >> index 8a7d546..ba8471f 100644
> > >> --- a/drivers/vfio/pci/vfio_pci_private.h
> > >> +++ b/drivers/vfio/pci/vfio_pci_private.h
> > >> @@ -83,6 +83,8 @@ struct vfio_pci_device {
> > >> bool bardirty;
> > >> bool has_vga;
> > >> bool needs_reset;
> > >> + bool aer_recovering;
> > >> + struct completion aer_completion;
> > >> struct pci_saved_state *pci_saved_state;
> > >> int refcnt;
> > >> struct eventfd_ctx *err_trigger;
> > >> --
> > >> 1.8.3.1
> > >>
> > >>
> > >
> > > How about some explanation about what is going on here? All these
> > > changes seem racy since any number of errors can trigger at any time.
> > >
> >
> >
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